Numbers will round in Excel even if you think you have set the number of decimals but you can control this feature by setting the option Precision as Displayed. 

1.  Click on the Microsoft Office Button.
2.  Click Excel Options, and then the Advanced option.
3.  Look for When calculating this workbook, select Set precision as displayed check box.
4.  Click OK until you exit the Excel Options.

This should do the trick.  Ofcourse you can always use the ROUND function to round the numbers.